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      <td class="headertitle">M-File Help: Tracker</td>
      <td class="subheader-left"><a href="matlab:open Tracker">View code for Tracker</a></td>
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<h1>Tracker</h1><p><span class="helptopic">Track points in image sequence</span></p><p>
This class assigns each new feature a unique identifier and tracks it
from frame to frame until it is lost.  A complete history of all
tracks is maintained.

</p>
<h2>Methods</h2>
<table class="list">
  <tr><td style="white-space: nowrap;" class="col1"> plot</td> <td>Plot all tracks</td></tr>
  <tr><td style="white-space: nowrap;" class="col1"> tracklengths</td> <td>Length of all tracks</td></tr>
</table>
<h2>Properties</h2>
<table class="list">
  <tr><td style="white-space: nowrap;" class="col1"> track</td> <td>A vector of structures, one per active track.</td></tr>
  <tr><td style="white-space: nowrap;" class="col1"> history</td> <td>A vector of track history structures with elements id and uv
which is the path of the feature.</td></tr>
</table>
<h2>See also</h2>
<p>
<a href="matlab:doc PointFeature">PointFeature</a></p>
<hr>
<a name="Tracker"><h1>Tracker.Tracker</h1></a>
<p><span class="helptopic">Create new Tracker object</span></p><p>
<strong>T</strong> = <span style="color:red">Tracker</span>(<strong>im</strong>, <strong>C</strong>, <strong>options</strong>) is a new tracker object.  <strong>im</strong> (HxWxS) is an
image sequence and <strong>C</strong> (Sx1) is a cell array of vectors of PointFeature
subclass objects.  The elements of the cell array are the point features
for the corresponding element of the image sequence.

</p>
<p>
During operation the image sequence is animated and the point features
are overlaid along with annotation giving the unique identifier of the
track.

</p>
<h2>Options</h2>
<table class="list">
  <tr><td style="white-space: nowrap;" class="col1">'radius', R</td> <td>Search radius for feature in next frame (default 20)</td></tr>
  <tr><td style="white-space: nowrap;" class="col1">'nslots', N</td> <td>Maximum number of tracks (default 800)</td></tr>
  <tr><td style="white-space: nowrap;" class="col1">'thresh', T</td> <td>Similarity threshold (default 0.8)</td></tr>
  <tr><td style="white-space: nowrap;" class="col1">'movie', M</td> <td>Write the frames as images into the folder M as
with sequential filenames.</td></tr>
</table>
<h2>Notes</h2>
<ul>
  <li>The 'movie' options saves frames as files NNNN.png.</li>
  <li>When using 'movie' option ensure that the window is fully visible.</li>
  <li>To convert frames to a movie use a command like:</li>
</ul>
<pre style="width: 90%%;" class="examples">
ffmpeg&nbsp;-r&nbsp;10&nbsp;-i&nbsp;%04d.png&nbsp;out.avi
</pre>
<h2>See also</h2>
<p>
<a href="matlab:doc PointFeature">PointFeature</a></p>
<hr>
<a name="char"><h1>Tracker.char</h1></a>
<p><span class="helptopic">Convert to string</span></p><p>
<strong>s</strong> = T.<span style="color:red">char</span>() is a compact string representation of the <span style="color:red">Tracker</span> parameters and status.

</p>
<hr>
<a name="display"><h1>Tracker.display</h1></a>
<p><span class="helptopic">Display value</span></p><p>
T.<span style="color:red">display</span>() displays a compact human-readable string representation of the
<span style="color:red">Tracker</span> object

</p>
<h2>Notes</h2>
<ul>
  <li>This method is invoked implicitly at the command line when the result
of an expression is a Tracker object and the command has no trailing
semicolon.</li>
</ul>
<h2>See also</h2>
<p>
<a href="matlab:doc Tracker.char">Tracker.char</a></p>
<hr>
<a name="plot"><h1>Tracker.plot</h1></a>
<p><span class="helptopic">Show feature trajectories</span></p><p>
T.<span style="color:red">plot</span>() overlays the tracks of all features on the current <span style="color:red">plot</span>.

</p>
<hr>
<a name="tracklengths"><h1>Tracker.tracklengths</h1></a>
<p><span class="helptopic">Length of all tracks</span></p><p>
T.<span style="color:red">tracklengths</span>() is a vector containing the length of every track.

</p>
<hr>

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  <tr class="subheader" valign="top"><td>&nbsp;</td></tr></table>
<p class="copy">&copy; 1990-2012 Peter Corke.</p>
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